PROJECTSUMMARY/ABSTRACT: Identifying host determinants governing HIV transcription and latency is critical to developing an HIV cure. Cell-surfaceglycosylationandlectin-glycansignalingplaycriticalrolesintheestablishmentofseveralimmune responses and modulation of cell-cell and cell-pathogen interactions. The relevance of host glycosylation machinerytoHIVlatencyisyettobedetermined.Weperformedapilotexperimentinvolvingtheapplicationof cutting-edgetechnologiestocharacterizetheglycanstructureprofilesonthecellmembranesofHIVlatently- infected, productively-infected, and uninfected primary CD4+ T cells (obtained by infecting primary CD4+ T cells with a dual-fluorescence HIV reporter construct which enables the identification, quantification, and FACS-basedpurificationofthesecellularpopulations).Ourpilotexperimentstronglysupportsthehypothesis that latently-infected primary CD4+ T cells harbor a distinct glycomic profile, as compared to productively- infected or uninfected cells. Furthermore, we recently demonstrated that the human carbohydrate-binding protein galectin-9 (Gal-9) regulates HIV transcription and potently reactivates latent HIV in vitro and ex vivo. Gal-9 signals through cell-surface N-linked glycans in vitro, modulating key transcription initiation and chromatin remodeling factors that regulate HIV latency. Our data reveal that host glycan structures on the surfaceofinfectedcellsmaymediatesignalsthatdefinethetranscriptionalstateofHIV,andsuggestthatGal- 9andthehostglycosylationmachineryshouldbeexploredasfoundationsfornovelstrategiestocureHIV. Aim 1 of our proposal will utilize a primary cell-based model to rigorously determine if HIV latently-infected CD4+cellsexhibitadistinctglycomicfingerprintthatcanbeexploitedtoidentifyandtargetHIVlatency.We will infect primary CD4+ T cells isolated from 40 HIV-uninfected donors with a dual fluorescent reporter HIV construct allowing the differentiation and purification of latently-infected, productively-infected, and uninfected cells.WewillidentifyglycanpatternsassociatedwithHIVlatencybyprofilingthecell-surfaceglycanstructures ofeachpopulationusinganadvanced,high-densitylectinmicroarrayplatform.InAim2,wewilldecipherthe nature of glycan-mediated recognition in Gal-9-mediated reversal of HIV latency. First, cell-surface glycan patterns of purified HIV latently-infected primary CD4+ T cells will be correlated with the ability of Gal-9 to reverseHIVlatencyinvitro.Then,wewilluseenzymaticdeglycosylationtoexaminetherequirementofcell- surface N-linked and O-linked glycans in Gal-9-mediated viral reactivation ex vivo in primary CD4+ T cells isolatedfromHIV-infectedART-suppressedindividuals.Thisstudywillallowustodefinetheopportunitiesby whichglycan-basedinterventionscanbeharnessedtoidentifyanderadicateHIVinfection.